This invention relates to a bag-making machine for fabricating bags from thermoplastic material of tubular flexible feed stock. More particularly the invention relates to an improved discharge apparatus for facilitating the removal and stacking of finished bags from a bag-making machine.
It is known to form bags from tubular feed stock of thermoplastic material such as polyethylene or polypropylene by advancing a flattened tube of the stock downstream to a station at which the opposed sides of the stock are sealed together by the application of heat and pressure. Concurrently with the sealing operation, the stock is cut adjacent the seal for severing each formed bag from stock upstream of the station. The finished bags are then discharged from the station and are projected across a gap to a stacking table by means of stacking wheels alone or in combination with opposed conveyor belts disposed intermediate the said station and stacking wheels.
In order to ensure that a continuous uninterrupted stream of newly formed bags are projected by the discharge apparatus onto the stacking table, precise control over the operation of the apparatus is desirable. The discharge apparatus should be precisely timed to operate immediately or shortly after the sealing and cutting operations to ensure a satisfactory rate of throughput of feed stock and discharge of newly formed bags. The discharge apparatus should also operate for a sufficient length of time to accelerate each newly formed bag away from the machine and the manner in which the bags are accelerated by the discharge means should be such that the bags, when they reach the stacking table, are arranged in condition for immediate packaging. Since the bags are quite limp they must be corrugated by the stacking wheels and ejected with sufficient momentum that they reach the stacking table in a flattened state. The bags must not, however, be ejected so rapidly that they overshoot the stacking table or they do not stack properly on the table and their discharge velocity must, therefore, be decelerated near the end of their travel.
Satisfactory operation of the discharge apparatus thus requires control over the correct timing of the apparatus in relation to the timing of the sealing-cutting apparatus, control over the length of time that the device is operative in each cycle and control over the velocity to which the newly formed bags are accelerated and from which they are decelerated by the apparatus. Few known devices provide means by which such control can be achieved and still fewer provide means whereby such control can be made while the bag-making machine is in operation.
It is the principal object of the present invention to provide a discharge apparatus for a bag-making machine having means permitting precise control over the velocity to which newly formed bags are discharged by the apparatus. Other objects of the invention ancillary to this object are a discharge apparatus having means for controlling the timing of the apparatus relative to the sealing-cutting cycle, and means for controlling the operation of the discharge apparatus during the said cycle.
It is another object to provide a discharge control means which may be operated while the bag-making machine is in operation whereby adjustments may be made in the discharge apparatus to ensure a continuous stream of bags to the stacking table without the necessity of shutting down the machine.
Another object is to provide control means which may be used in conjunction with most bag-making machines with only minor adjustments and which comprises only a small number of known and readily available components.